GB404011A - Improved magnetic compositions containing principally iron and cobalt - Google Patents

Abstract

Magnetic articles are made from an alloy containing 30-70 per cent of iron, and 70-30 per cent of cobalt, in which is incorporated 0.5-4 per cent of vanadium, or up to 3 per cent of manganese, or both vanadium and manganese, and which, preferably after limited mechanical working as by hot rolling, is annealed at about 850 DEG C., or higher, and cooled rapidly as by quenching in brine and ice. The alloy, after casting, is maintained at 1000 DEG C. for 3 hours, and rolled at 1000 DEG C. to a thickness of about 0.1 inch, with a reduction of 0.025 inch per pass, and an interval of 5 minutes after every two passes, to restore the temperature. Sheets containing not more than about 2 per cent vanadium are annealed at about 900 DEG C. for about 1 minute and quenched, the heat treatment and quenching being repeated three times in some cases. To sheets of higher vanadium content an anneal at about 850 DEG C.-950 DEG C. and a single quench are applied. From the heat-treated sheets rings and other shapes may be punched, and thin strips may be rolled for making stampings for small receiver diaphragms. Thin tape rolled to 0.006 inch thick or less may be quenched in air. To develop the magnetic properties, the sheets are pot annealed for 1 hour at about 900-1100 DEG C. in an electric furnace, if desired in vacuo or in hydrogen, and cooled in the furnace. A further re-heating to about 600 DEG C. for 15 minutes and quenching in air may produce a further improvement.